Included here is the Congo Basin, eastern Nigeria, eastern Cameroon and the islands of the Gulf of Guinea (Fernando Po, Principe, Sae Tome and Annobon)

Congolian semi-deciduous forest is now restricted to a few places such as the Loum Forest Reserve in Cameroon. These forests may once have been continuous with the semi-deciduous forest of Mount Cameroon. Their presence, however, is somewhat surprising in an area that receives up to 4 m of rain per annum when just 2 m is sufficient to support evergreen forest. Their occurrence seems more likely to relate to the free-draining nature of the underlying volcanic substrate. The main canopy trees include species of Triplochiton, Celtis adalfi-triderici and C. philippensis, while other characteristic trees include Celtis gomphophylla, C. zenkeri, Cyclicodiscus gabunensis, Khaya ivorensis, Milicia regia, Piptadeniastrum africanum, Sterculia oblonga, Terminalia superba and Trilepisium madagascariense. However, much of the undergrowth of these forests has been lost to human activities. Nevertheless, they still include several endemic plants such as Beilschmiedia crassipes (Lauraceae), Crotonogyne impedita (Euphorbiaceae), Memecylon griseo-violaceum (Melastamataceae), Microberlinia bisulcata (Fabaceae) and Thyrosalacia racemosa (Celastraceae). On the other hand, some of these appear to be very narrow endemics and may now be extinct.

References

Brenan, J. P. M. 1978. Some aspects of the phytogeography of tropical Africa. Annals of the Missouri Botanical Garden, 65: 437-474.

Campbell, D. G. & Hammond, H. D. 1989. Floristic Inventory of Tropical Countries. The New York Botanical Garden.

White, F. 1983. The Vegetation of Africa. UNESCO.